In a pillar structure for an automobile exemplified by the center pillar illustrated in FIG. 5, a center pillar 1 has an outer panel 11 having a substantially hat-shaped cross, section that opens toward the vehicle interior, and an inner panel 12 that is substantially shaped as a flat plate or has a shallow substantially hat-shaped cross section, at an orientation inverse to that of the outer panel 11. The outer panel 11 and the inner panel 12 make up a closed cross-section structure. Inside the pillar there is provided a pillar reinforcement 2 in the upper-to-lower direction of the pillar, the pillar reinforcement 2 having a substantially hat-shaped cross section and running along the inner face of the outer panel 11. The pillar reinforcement 2 strengthens the stiffness of the pillar (for instance, Patent document 1).
In FIG. 5, the reference numeral 3 denotes a rocker joined to the lower end of the center pillar 1.
At the lower portion of the center pillar 1 that opposes the bumper of another vehicle B during, a vehicle side collision, as illustrated in FIG. 6 (the figure illustrates a barrier used in a collision test), there is positioned a rear end of an impact beam 4 disposed in the front-rear direction at the lower portion in a front door D1 that opens and closes a front door opening frontward of the center pillar 1, and also there is disposed a hinge member 49, which hinges the front edge of a rear door that opens and closes the rear door opening in the rear of the center pillar 1.
During a side collision, therefore, a substantial collision load acts on the lower portion of the center pillar 1, via the hinge member 49 and the rear end of the impact beam 4. In this case, the pillar reinforcement 2 disposed in the pillar in the upper-to-lower direction of the pillar is not found to be strong enough to withstand the locally substantial acting force. The cross section of the pillar lower portion breaks down on account of the acting force. This results in collapse deformation in the vehicle width direction, as denoted by the virtual line in FIG. 6. Once collapse deformation occurs, resistance to the collision load may be lost, so that the lower portion of the pillar bends significantly into, a V-shape, and the entire pillar shifts in the vehicle width direction, thereby pressing the vehicle interior.
In FIG. 6, the reference numeral 7 denotes a roof side rail to which the upper end of the center pillar 1 is connected, 8 denotes a roof, and 9 a floor.
The stiffness of the pillar could be reinforced by thickening the plate of the pillar reinforcement 2, and/or by increasing pillar stiffness locally by way of a bulkhead that partitions a closed cross-section in the pillar in the upper-to-lower direction of the pillar, as disclosed in Patent document 2.
Patent document 2 discloses the feature of reinforcing the stiffness of an intermediate portion of a center pillar in the upper-to-lower direction of the pillar.
Patent document 1: Japanese Patent Application Publication No. 2003-127901 (JP-A-2003-127901)
Patent document 2: Japanese Patent Application. Publication No. 9-20267 (JP-A-9-20267)